Author Topic: Hantarex polo - what happens when you turn the xray pot? (Read 15007 times)

crash41301 · « **on:** February 25, 2012, 06:46:55 pm »

So I went to adjust vertical linearity on my 25" polo chassis. Without noticing, I accidentally turned the xray protection adjustment pot. Thinking it was the vertical adjustment pot I kept turning it because nothing was happening. Nothing did happen, and eventually I realized I was turning the wrong adjustment. I then adjusted the vertical linearity pot. Shortly afterwards my monitor started having wavy, strange displays. It eventually stopped turning on at all, and now I have no B+ on the power supply section.

I've tried a cap kit, new HOT and new flyback. No change. I tested at TP6 and have no B+ power. Any thoughts? I am thinking perhaps I tripped the Xray protection circuit? Strangely enough, occasionally the monitor will have power and fire up?

Appreciate any help you can provide!

grantspain · « **Reply #1 on:** February 25, 2012, 07:14:11 pm »

I have worked on an awful lot of polo chassis and never seen an x-ray protection pot,the only ones on the chassis are B+ and vertical linearity.Sometime there is a daughter board with trapezoid and pincushion pots.

Can you post of photo of the position of this pot-perhaps this is only on U.S release polo hence why I have not seen it before

crash41301 · « **Reply #2 on:** February 25, 2012, 07:23:32 pm »

Sure, here is a pic. Ignore the "what is it" on the right. I grabbed this pic from online. I circled the thing that says "Xray prot" on the board that I turned.

grantspain · « **Reply #3 on:** February 25, 2012, 07:30:04 pm »

yep not on european models

turn your x-ray pot anti clockwise to maybe 9 o'clock

next step is desolder pins 1 and 3 of the flyback transformer and connect a mains light bulb to the pad of pin 3 of the flyback and the other side of the bulb the flyback heatshield

then you can meter your B+ using a dummy load and prove if the issue is related to power supply or deflection

crash41301 · « **Reply #4 on:** February 25, 2012, 08:11:54 pm »

Excuse my ignorance, but what is a "mains light bulb"? Also, what is the flyback heatshield? Is that the large heat sink running around the flyback? Are you saying I should solder pin3 to a normal 120v light bulb hot and solder a wire from the lightbulb ground to the heat sink?

Lastly, which pin is 1 and 3? I attached a pic I found on the internet (My chassis doesnt look this bad! ) for reference.

Apologize for my ignorance on this. I can solder, but I've not tried attaching light bulbs to stuff before.

Drnick · « **Reply #5 on:** February 26, 2012, 04:54:21 am »

A Mains Lightbulb is a Lightbulb that runs off the mains. IE one of those that hangs from the ceiling. Basically a bulb that uses 110-240v rather then 5-12V.

grantspain · « **Reply #6 on:** February 26, 2012, 07:34:16 am »

lightbulb fixing points

crash41301 · « **Reply #7 on:** February 26, 2012, 05:51:01 pm »

Ah ha... I noticed something when I was going to do the soldering for the lightbulb!

C125 was still a daiwoo cap. It turns out that C125 wasnt changed when I did the cap kit. I looked over the list of caps in the kit and the 470uf 35V cap for C125 WASNT INCLUDED!! A quick look at the schematic and C125 is a power supply cap of some sort. So... a trip to radio shack (OMG they actually had one) and I swapped it just for the heck of it. Tada! I have power and some form of raster now

Now I have another problem though; I cant get a picture that's stable or shows anything. Its just a shakey white raster. I tried adjusting all of the knobs on the remote board, the controls on the flyback, and the Vlinearity. None of them seemed to do anything. There is also a high pitched whine noise coming from around the flyback. I attached a picture of what it looks like. Any idea?

grantspain · « **Reply #8 on:** February 26, 2012, 06:22:11 pm »

did you get the wires to screen volts and focus correct when you swapped the flyback,also whats the number of the new flyback-focus wire is normally heavier gauge wire of the two that goes into the crt socket itself
should be a hr7191 or equiv

crash41301 · « **Reply #9 on:** February 26, 2012, 07:05:57 pm »

Numbers written on the side of the flyback are 01-0250. I have a thicker black wire coming from the flyback going to the neck socket. I have a red wire coming from the flyback going to W1.

It seems like the high pitched noise fluctuates with the random waveyness and flicker on the screen?

Also measured B+ at TP6 and its 131V per my multimeter. I used the monitor frame as ground for the test.

Any thoughts? Btw, I want to thank you for all your help thus far!

grantspain · « **Reply #10 on:** February 26, 2012, 07:55:17 pm »

B+ is almost spot on at 131vdc

when you adjust the screen volts on the flyback does it have any affect on the brightness at all?

if not we are looking at some blanking issue and you will need to check a few resistors and i guess you remembered to reconnect the neck card earth

crash41301 · « **Reply #11 on:** February 26, 2012, 08:42:49 pm »

I can make the screen really bright or really dim with the "screen" control on the flyback. I messed with the focus knob and I can also make the funky looking white screen more or less focused too. Seems like the flyback is working?

Also, I noticed that if I play with the remote adjust card I can make the high pitched noises coming from around the flyback all but go away. I dont know if that helps diagnose or not

grantspain · « **Reply #12 on:** February 27, 2012, 02:39:33 am »

if you coin up do you get game sounds?

crash41301 · « **Reply #13 on:** February 27, 2012, 09:46:35 am »

Yep, I can coin up and I can hear the game in attract mode too. I swapped to another known working Jamma PCB just to verify it wasnt the PCB giving out a bad signal and it suffers from the same problem in this cab.

grantspain · « **Reply #14 on:** February 27, 2012, 02:05:55 pm »

i would look at ic1 on the neck card lm1203n and check 200vdc at r40

crash41301 · « **Reply #15 on:** February 27, 2012, 03:05:16 pm »

Thanks Grant. Going to check R40 when I get home today. I actually ordered an LM1203 and a socket the other day so I guess I'll wait for that to get here and swap it out if R40 doesnt show 200v DC.

Again, big thanks for your guidance!

grantspain · « **Reply #16 on:** February 27, 2012, 04:10:16 pm »

also check R233,R239,R236 all near the flyback R36,R35 and R40 itself on the neck card
check using ohm setting on multimeter and i would suggest lifting one leg out of circuit in case of ghost readings

crash41301 · « **Reply #17 on:** February 27, 2012, 10:55:30 pm »

Wow the ones next to the flyback were a PITA to get to! I lifted at least one side on each, most of them I just pulled it completely off the PCB and held it in my hands with the multimeter. Here is what I got:

R40 = 10.1 - Should be 10.5
R36 = 266 - Should be 270
R35 = 1.0 - Should be .75

R236 = 1.2 - Should be "1R"
R233 = 199.8k - Should be 100k
R239 = 469k - Should be 470k

Seems like all are within margin of error with the exception of R233, seems way too high? I see in the schematic that its supposed to be 100k? Thoughts on that? I assume I should throw a 100k resister in there since it seems to be off by almost double the stated rating.

the 200v DC on R40, how would I test that? I hooked the chassis back up and powered it on. I then attached my multimeter ground to the monitor frame, set my meter to 600v DC range and touched the solder side of the neck board on one side of R40. I got nothing. I then touched my meter to the other side of R40, also nothing. Am I doing the test right?

grantspain · « **Reply #18 on:** February 28, 2012, 03:33:04 am »

sound slike the 200vdc is the problem,download the schematics and trace the 200v line back to the flyback checking any resistors on the way,R234 10 ohm,D137 DIODE,C177 and R235

crash41301 · « **Reply #19 on:** February 28, 2012, 10:30:40 pm »

R234 = Way out of tolerance
R235 = 175k, out of tolerance some, but close. Probably warrants replacement
D137 = Shows continuity with polarity one way, but not the other way (this means its good, right?)
C177 = Brand new as part of the Cap kit I installed, shows continuity from the connections to the next leg in the trace for both legs. Should be ok?

I am thinking I replace R234 and R235 and cross my fingers?

grantspain · « **Reply #20 on:** February 29, 2012, 01:12:41 am »

diode sounds ok,resistors were read with one leg lifted from circuit?

crash41301 · « **Reply #21 on:** February 29, 2012, 08:54:40 am »

Resisters read completely removed from the board. (Really hard to get a multi-meter in there otherwise IMO)

Is there a way to test the new cap with my multi-meter? I looked online but I only saw where people were testing using what appeared to be a cap tester.

grantspain · « **Reply #22 on:** February 29, 2012, 12:25:45 pm »

need a esr meter to read a cap,well something that reads farads

crash41301 · « **Reply #23 on:** February 29, 2012, 01:41:05 pm »

Picked up 2 new resisters at radio shack today. Tonight I'm going to try swapping them into R234 and R235. R234 was supposed to be a reading of 10, but was a reading of 600k+ or something really really high. I am wondering if that might be restricting the flow of voltage down to essentially nothing at the neck board. I figure if the voltage is starting at around 238vDC it doesnt need much resister to get to 200vDC, right? 600k+ should restrict it tremendously?

Crossing my fingers that this might be it!

grantspain · « **Reply #24 on:** February 29, 2012, 01:48:49 pm »

it does sound the likely culprit-good luck

crash41301 · « **Reply #25 on:** March 01, 2012, 12:00:26 am »

So I learned a valuable lesson tonight: Blue resistor's are NOT just blue for no reason.

I installed a normal 1/2 watt 10 ohm into R234. I started smelling something burning and quickly turned the monitor off. It started burning the new resistor up. It appears the rest of the board is ok though. Hopefully it is! WTF happened I thought?? So I started looking at the schematic and realized that this was something called a "flame proof" resistor, not a 1/2 watt. Crap!

I did decipher a few things before the burning smell became obvious. R40 had about 160v DC on it with the new resistor, which is of course different that the 0v DC it previously had. The screen seemed to be the exact same though.

I also got my LM1203 in the mail. Since the monitor worked identically with the new resistor (at least for the 30 seconds I had it on before smelling burning resistor) I went ahead and socketed the LM1203 and installed the new LM1203. I've got the old one as well so I can swap it into the socket too if it acts weird with the new one.

Tomorrow - back to radio shack to see if they have "flame proof" 10 ohm resistors for R234. If not I guess I am going to end up ordering one from Mouser, but it really sucks to pay $5 shipping for a .98 cent part. lol. Will update once I have something to update with. I am determined to get this thing working as long as you are willing to aim me places.

MonMotha · « **Reply #26 on:** March 01, 2012, 12:30:32 am »

Actually, Digi-Key is cheaper than Mouser these days on really low dollar orders. They axed their handling fee, and they'll do USPS first class with no delivery confirmation. I think I've gotten it down to about $3, but YMMV.

The flameproof rating shouldn't really affect normal operation. It sounds like that part was dead because it died to protect something else on the monitor. It's essentially being used as a fuse, hence the flameproof rating. When you replaced it, it started protecting things again (by getting really hot).

grantspain · « **Reply #27 on:** March 01, 2012, 02:29:16 am »

when you get your new flame proof lift one side of r40 before turning on the monitor
recheck polarity of c177

crash41301 · « **Reply #28 on:** March 01, 2012, 10:59:26 pm »

What wattage is R234? All I can figure out is that it is "flame proof". Size wise it seems like it would be 1/2 watt?

Would something like this work? I dont see any 1/2 watt resistors on digikey.
http://search.digikey.com/us/en/products/RSF100JB-10R/10W-1-ND/18035

grantspain · « **Reply #29 on:** March 02, 2012, 02:11:10 am »

you could use 0.5 watt.0.75 watt or 1 watt

crash41301 · « **Reply #30 on:** March 02, 2012, 11:42:35 am »

Scored some flame proof resisters locally today

Going to install, lift R40 and measure.

I also checked the polarity of C177, it was right per the markings on the board. Any other thoughts on places to check that might be causing badness?

grantspain · « **Reply #31 on:** March 02, 2012, 01:29:02 pm »

Quote from: crash41301 on March 02, 2012, 11:42:35 am

Scored some flame proof resisters locally today Going to install, lift R40 and measure.

I also checked the polarity of C177, it was right per the markings on the board. Any other thoughts on places to check that might be causing badness?

possibly shite flyback-people go one about never had a bad flyback from new but some of this rubbish being knocked up in china is a fire hazard

crash41301 · « **Reply #32 on:** March 02, 2012, 10:56:13 pm »

No luck tonight.

I got a new R234 installed, and I removed R40. Hooked up the chassis, fired it up and no burning smells. Well, thats good. So I whipped out the multimeter and measured the voltage at R40. Its only 131V. Ironically, this corresponds to what my TP6 was previously. As a point of data, the screen looks identical with R40 removed from the circuit.

I then measured voltage at TP33 so see if perhaps it was R235 causing havoc. Voltage is approximately the same at TP33. I sat and looked at the schematic for a while. It pretty clearly says this should be 200V. I see your comment about a bad new flyback, so I desoldered the new one and put the old one back on. (The old one was working just fine before, just changed it as preventative / shotgun) I then hooked everything up and measured at TP33. Ive got the same 131V. I assume this means that my new flyback is good? (That or both flybacks are suffering from the same problem anyway?)

I am thinking I should be measuring the voltage going into the flyback at this point? I am thinking if the voltage is low going into the flyback then it would naturally be low coming back out of the flyback? It looks like power goes into pin 3 on the flyback per the schematic. Is that AC or DC voltage? If DC, can I do something as simple as touch pin 3 on the flyback with the multi-meter lead while its powered up?

Any other thoughts?

grantspain · « **Reply #33 on:** March 03, 2012, 07:02:19 pm »

yeah read the b+, dc volts 200 range-black probe to flyback heatshield and red probe to pin 3-you should get 105-110v

watch yourself with this,110vdc is a nasty voltage

yeah looks like your new flyback is ok

crash41301 · « **Reply #34 on:** March 03, 2012, 07:32:15 pm »

Is the flyback heat shield the giant heat sink running around the flyback? If not, what is it?

grantspain · « **Reply #35 on:** March 04, 2012, 05:00:10 am »

Quote from: crash41301 on March 03, 2012, 07:32:15 pm

Is the flyback heat shield the giant heat sink running around the flyback? If not, what is it?

yes

crash41301 · « **Reply #36 on:** March 04, 2012, 12:28:50 pm »

Looks like I am getting 131vDC at pin 3 on the flyback.

I measured it by soldering a wire to pin 3 and hanging the wire out so I could hook up the chassis. I then clipped my negative to the heat sink and touched the wire with my positive.

I have another observation though, I noticed that at first the voltage at R40 was 175vDC. After a few moments it seemed to jump down to 130vDC or so. I still have R40 unhooked, could it be some sort of feedback loop that is kicking the voltage down because it notices R40 isnt hooked up?

grantspain · « **Reply #37 on:** March 04, 2012, 12:49:50 pm »

oh yeah reconnect r40 and see what happens

crash41301 · « **Reply #38 on:** March 04, 2012, 01:52:33 pm »

R40 hooked back up into circuit. Turned on the machine and the same screen showed up. Argh! I tired not to get too hopeful, but I did anyway. lol.

I went to measure at R40 and got no voltage. Also got no voltage at R234. I wonder if something beyond R40 is shorted?

grantspain · « **Reply #39 on:** March 04, 2012, 02:09:09 pm »

what value cap do you have at c177,should be 47uf 250v-also cap at c14 neckcard should be 4.7uf at 250v


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